A system-on-chip digital pH meter for use in a wireless diagnostic capsule

Area of Science:

• Biomedical Engineering
• Microelectronic Systems
• Chemical Sensing

Background:

• Wireless capsule endoscopy requires miniaturized, integrated sensors for in-situ measurements.
• Traditional pH meters often lack the integration and power efficiency needed for capsule applications.
• Developing a single-chip solution is crucial for reducing size and complexity.

Purpose of the Study:

• To design and implement a system-on-chip (SoC) digital pH meter tailored for wireless capsule applications.
• To integrate key analog and digital components onto a single chip for enhanced functionality and reduced external connections.
• To achieve a high-resolution digital output for accurate pH monitoring within a capsule environment.

Main Methods:

• The system is architected around an 8-bit microcontroller functionally equivalent to the Motorola 6805.
• An ion-sensitive field-effect transistor (ISFET) with a floating electrode forms the core of the analog subsystem.
• The design utilizes a commercial CMOS process, incorporating on-chip programmable voltage references and multiplexors for flexibility.

Main Results:

• The single-chip pH meter demonstrates a high resolution of 37 bits/pH.
• The device operates effectively within a 7 pH unit range.
• The modular design facilitates verification and component re-use, streamlining development.

Conclusions:

• The developed SoC digital pH meter is suitable for integration into wireless capsule endoscopy systems.
• The chip's design offers a compact, flexible, and high-resolution solution for in-vivo pH monitoring.
• This advancement paves the way for more sophisticated diagnostic tools in gastrointestinal applications.